The present invention relates to the video processing arts. It finds particular application in conjunction with the display of images from computed tomography (CT) diagnostic scanners and will be described with particular reference thereto. However, it is to be appreciated that the invention will find further application in other areas of medical diagnostic imaging, quality assurance imaging, and other video applications, particularly those in which a wide range of gray scale differentiation is advantageous.
CT images, which have a high spatial resolution and a good signal-to-noise ratio, have traditionally been displayed on monochrome monitors. Monochrome monitors provided better resolution than color monitors whose color masks tend to cause spatial distortions. On the other hand, color monitors are most commonly used in nuclear medicine in which the spatial resolution was significantly lower than in CT. The color monitors allow the viewer more accurate quantification. The human eye can distinguish hundreds of color and hue tones but only about twenty gray scale levels.
In xenon-CT, magnetic resonance spectroscopy, magnetic resonance and CT flow imaging, and the like, a variety of different types of images are commonly produced. For some of the images, the resolution of a monochrome display is more desirable. For other images, the more accurate quantification of a color monitor would be desirable. However, the entire family of images in these studies is normally displayed on one monitor--a monochrome monitor which preserves the resolution of the highest resolution images.
Color imaging is also more expensive. CT scanners conventionally include a monochrome video processor which generates the output video signal. Changing to color would require not only a more expensive color video processor, but would also require extensive modifications to interacting software and hardware. This redesign would add tens of thousands of dollars to the cost of CT scanners. The extensive amount of rebuilding and modification of software, firmware, and hardware would make retrofitting existing CT scanners impractical.
The present invention enables a standard monochrome video signal to be displayed in monochrome, color, or a combination of monochrome and color.